In recent years, there has been increased interest in integration of metal nanoparticles with carbon nanotubes (CNTs) owing to the structural, electrochemical and catalytic properties of the CNTs. The ability of carbon nanotubes to support inorganic nanoparticles such as metal, metal oxides and metal alloy nanoparticles offers opportunities to synthesize hybrid materials that may be used in applications such as for energy conversion (such as, in fuel cells and photo voltaic cells), storage (such as, supercapacitor and lithium ion battery), field emission displays, and gas and vapor sensors.
Some conventional techniques for synthesis of CNTs decorated with metal nanoparticles include surface functionalization of purified CNTs by vigorous acid treatment and chemical reduction and/or oxidation of metal salts using strong reducing/oxidizing agents or by electrodeposition of metal nanoparticles on CNTs. Such techniques may require use of harsh and toxic chemicals thereby limiting the use of the hybrid materials for certain applications. Moreover, some of the techniques require multiple processing steps for forming the hybrid materials and may need intensive energy, thus making them challenging for large scale preparation. In some of these techniques, there are additional costs associated with use and removal of the solvents and the reducing reagents.
Metal salts are commonly used as precursors for depositing metal nanoparticles on chemically inert graphitic surface of the CNTs. However, current synthesis techniques may cause destruction of the CNT structures and therefore change their intrinsic electronic and mechanical properties. Further, inorganic coatings on acid-treated CNTs are often non-uniform.
Some hybrid structures formed by integration of CNTs and metal nanoparticles are used for environmental, defense, biological and medical applications. Such hybrid structures can be used as sensors for detecting organophosphorus compounds. One such organophosphorus compound is paraoxon that may be used as chemical warfare agent due to its high toxicity towards mammals causing neurological disorders. Some of the current detection techniques include gas chromatography, high performance liquid chromatography, and spectroscopy. Many of these techniques are tedious, time consuming and are substantially expensive.